This invention relates to an intracorporeal microwave warming method and means. It relates more particularly to microwave apparatus including a catheter capable of being introduced into a patient's blood vessel or body cavity to provide uniform and controlled heating of fluid or tissue within the patient. The invention has particular application as an intravascular blood warmer for raising the body core temperature of a hypothermic trauma patient and so the invention will be described primarily in that context. It should be understood, however, that aspects of the invention have equal application in other contexts such as benign prostatic hyperplasia (BPH) ablation and myocardial ablation.
Hypothermia in trauma patients (i.e., body core temperature less than 35.degree. C.), has been shown to be associated with high mortality. According to studies, trauma patients having a temperature less than 34.degree. C. have a 60% mortality and those patients with a temperature less than 32.degree. C. have a 100% mortality. The effects of hypothermia on trauma patients are numerous. For example, a decrease in core temperature results in decreased mental status, decrease heart rate and cardiac output and diminished renal blood flow. Hypothermia also results in prolonged clotting times and portal sequestration of platelets causing peripheral thrombocytopenia as well as decreased platelet function. The resultant coagulopathy may make futile all attempts at surgical control of traumatic bleeding.
There are currently several methods of rewarming a trauma patient in general use today. These include use of warm resuscitation fluids, airway rewarming, heating blankets, overhead radiant warmers, body cavity lavage, continuous arteriovenous rewarming (CAVR) and cardiopulmonary bypass. The most effective method of rewarming is currently cardiopulmonary bypass, but this technique is often unavailable and is technically difficult to perform. CAVR has been shown to be much more efficient than other standard rewarming techniques, but it requires cannulation of both the femoral artery and vein in order to connect the patient to a conventional external heat exchanger and it is somewhat work intensive. Furthermore, it results in loss of blood because a considerable amount of fluid is required in order to fill up or prime the various IV tubes connected to the warmer.
It would be desirable, therefore, to be able to provide a simple, efficient means of rewarming trauma patients, especially soldiers in combat who are significantly injured and therefore at risk for developing. Controlled intracorporeal heating for other reasons is also a desirable objective.